What is extension ID?

After selecting a module and right-clicking it and choosing “New Extension,” an extension editor comes up. In that window, there is an icon under the menu items whose mouse-over says “Extension Properties.”

In that Extension Properties window, there’s something called “Extension ID” with a button next to it called “Change.” What’s the significance of the Extension ID–what does it do, and when would I want to change it? Does it relate to the .vmod file extension of the module extension? (I’m guessing no, but I’d like to make sure.)

The extension id is used as part of the Unique Id that identifies what gamePiece definition generated a counter. It is saved as part of the unit definition in saved files. There is a new tool included in version 3.2 which allows you to update all pieces you own in a game with the current definition of that piece. If you change the Extension Id, this tool will not be able to update the pieces.